Defending champion Andy Roddick of the United States and Croatia's Ivo Karlovic have advanced to the finals of the Stella Artois grass-court tennis tournament in London.

Roddick, the second seed, defeated fourth-seeded Radek Stepanek of the Czech Republic in three sets 6-3, 2-6, 6-2.

After breaking Stepanek's serve early in the first set Saturday, Roddick hit a slump in the second set before getting back on track for the victory.

The 22-year-old Roddick faces Karlovic, who scored a straight-set win over sixth-seeded Thomas Johansson of Sweden 6-4, 7-6. The two meters, eight centimeter tall Karlovic fired 19 aces on his first serve in the one hour, 24 minute match.

Roddick and Karlovic have never met one another before in ATP Tour play. The tournament is a key warmup for Wimbledon -- the third Grand Slam event of the season.

Some information for this report provided by AP.